1. Field of the Invention
The invention relates to an improved apparatus for gravel packing a screen and the adjoining perforated production zone of a subterranean well.
2. History of the Prior Art
Apparatus for effecting the gravel packing of a screen and the adjoining perforated production zone of a subterranean well is well known in the prior art. For example, see the 1982-1983 Catalog issued by BAKER SAND CONTROL, a Division of BAKER OIL TOOLS COMPANY of Houston, Tex. In this catalog there are disclosed typical gravel packing apparatuses and, on pages 8 and 9 of the catalog, there is described a conventional sequence for effecting the gravel packing and related operations such as squeezing and reverse flow.
In the apparatus disclosed in the aforementioned catalog, a liner assemblage is connected in depending relationship to a settable packer. The packer in turn is run into the well by a conventional setting mechanism which is connected to the bottom end of a tubular production string or work string. The tubular liner assemblage includes one or more screen which, when the apparatus is properly positioned in the well, are located adjacent the perforated production zone. The packer is then set in that position.
A gravel packing apparatus, including a conventional crossover tool, is supported in depending relationship to the packer setting mechanism and includes a wash pipe which extends downwardly through the liner assemblage and terminates at a position below or adjacent the screen. The gravel packing operation then proceeds in conventional fashion with a slurry containing the gravel being pumped down the tubular string and passed through the central bore of the set packer in the crossover tool. Below the packer seal, the gravel carrying slurry is directed outwardly through cooperating radial ports provided in the crossover tool and the adjacent portion of the liner, and flows downwardly through the annulus defined between the liner and the interior of the well casing to pile up above a sump packer or similar casing annulus sealing element or well bottom until the layer of deposited gravel covers the screen and the adjoining casing perforations. If desired, a squeezing operation can then be performed to apply pressure to the deposited gravel to force it outwardly into the perforations in the adjoining production formation. A return path for the liquid component of the gravel carrying slurry is provided by the screen and the open bottom end of the wash pipe, and this liquid component, together with any particulate matter which was small enough to pass through the screen, is flowed upwardly to the well surface through the outer passages conventionally provided in the crossover tool.
There comes a time, however, when the gravel packing and related operations are completed and the gravel packing apparatus, including the wash pipe, must be removed from the well. During this removal operation, particulate matter contained in the fluid remaining in the lower portions of the wash pipe and the crossover element of the gravel packing apparatus are free to flow downwardly into the well perforations. Also any fluids and particulates in the casing annulus above the set packer can flow into the bore of the liner assemblage and penetrate the production formation.
A principal object of this invention is to provide a reliable, automatically operating valving apparatus for effecting a complete seal of the bore area of the liner assemblage above of the screen element upon the withdrawal of the wash pipe, thus protecting the screen and the adjoining production formation from penetration by undesirable fluids and particulate matter.